Process of introducing ashing ingredients into oxidized cellulose material intended as smoking product and product obtained thereby

ABSTRACT

A method of making a smoking product formed of oxidized cellulosic material is disclosed in which incorporation of ash forming components is effected in the form of mineralizing agents preferably developed in situ internally of the oxidized cellulosic fibers by treatment first with a calcium compound in aqueous medium and then with oxalic acid to form insoluble calcium oxalate in situ or by treatment of the cellulosic materials with the freshly mixed components which remain soluble in admixture for a length of time sufficient for internal absorption into the oxidized cellulosic system.

United States Patent [72] Inventors Theodore S. Brlskin;

Geoiirey R. Ward, both of Beverly Hills,

Calif.

2 l 1 Appl. No. 745,370

[22] Filed July 17, 1968 [45] Patented Sept. 28, 1971 I73] AimigneeSutton Research Corporation Los Angelea, Calli.

Continuation-impart 01 application Ser. No. 595,622, Nov. 21, 1966,Patent No. 3,447,539, and a continuation-impart 01 674,994, Oct. 12,1967, now abandoned.

[54] PROCESS OF INTRODUCING ASIIING INGREDIENTS INTO OXIDIZED CELLULOSEMATERIAL INTENDED AS SMOKING PRODUCT AND PRODUCT OBTAINED THEREBY 23Claims, No Drawings [51] Int. Cl ...A24b 15/00 [50] FieldoiSeai-ch 131/Primary Examiner-Melvin D. Rein Attorney-McDougall, Hersh, Scott & LaddABSTRACT: A method of making a smoking product formed of oxidizedcellulosic material is disclosed in which incorporation of ash formingcomponents is effected in the form of mineralizing agents preferablydeveloped in situ internally of the oxidized cellulosic fibers bytreatment first with a calcium compound in aqueous medium and then withoxalic acid to form insoluble calcium oxalate in situ or by treatment ofthe cellulosic materials with the freshly mixed components which remainsoluble in admixture for a length of time sufi'icient for internalabsorption into the oxidized cellulosic system.

PROCESS OF INTRODUCING ASlllING INGREDIENTS INTO OXIDIZIED CELLULOSEMATERIAL INTENDED AS SMOKING PRODUCT AND PRODUCT OBTAINED THEREBY Thisis a continuation-impart of our copending application Ser. No. 595,622,filed Nov. 21, 1966, now US. Pat. No. 3,447,539, and entitled OxidizedCellulose Smokable Product including Ashing Ingredient, and Ser. No.674,994,

filed Oct. 12, 1967, now abandoned, and entitled Smoking Products andProcess for Making Such Products.

' As used herein, the term smoking products is meant to refer to and toinclude filler material embodied in cigarettes,

cigars and for use with pipes and the like, and mixtures thereof withvarious proportions of tobacco and including cigarette papers andwrappers used in the preparation of such cigars and cigarettes, and itincludes cigarettes, cigars and the like products manufactured with suchfiller materials and wrappers.

In the aforementioned copending applications, description is made of thepreparation of a smoking product suitable for use in cigarettes, cigarsor with pipes wherein the smoking product is prepared of relatively purecellulosic materials subjected to selective oxidation with liquidnitrogen dioxide to convert preferably more than 90 percent of themethylol groups in the cellulosic molecule to yield a product which canbe referred to as an oxycellulose or polyuronic acid. The oxidationreaction product is further processed by removal of liquid nitrogendioxide by vaporization and preferably by washing the oxidizedcellulosic product with water and/or alcohol and/or acetone or othersolvent for removal of solubilized foreign material, including oils,waxes, latices and the like, which contribute undesirably to the tasteand aroma when used as a smoking product in accordance with the practiceof this invention.

As further described in the aforementioned copending applications, theoxidized and cleansed cellulosic derivative is further processed by areduction reaction with borohydrides of an alkali or alkaline earthmetal such as sodium or lithium borohydride for reduction of suchnitrogen compounds, quinones, ketones, aldehydes and unsaturates asotherwise have a tendency to impart undesirable aroma and taste as thesmoking product is burned. The product before or after reduction can besubjected to additional oxidation with a dilute peroxide solution as ameans for eliminating further groupings which impart undesirable aromaor taste to the product.

The resulting smoking product is then formulated with mineralizingagents such as oxalates, glycolates, diglycolates, lactates, pivalatesor tannates of such metals as calcium, magnesium, lithium, potassium,barium or strontium, preferably introduced to form the salt internallyin the cellulosic derivative for purposes of providing desired ashingcharacteristics. instead of forming the described salts internally inthe cellulosic derivative, beneficial characteristics can be achieved byexternal application of such mineralizing agents. As described, thedesired internal introduction is achieved by first wetting thecellulosic derivative with metal cation in dilute solution forabsorption into the cellulosic derivative followed by exposure to theacid anion in solution to precipitate the metal salt in situ in thecellulosic material.

The treated cellulosic derivatives can be further processed to improvethe burning, glow and smoking characteristics by the formulation toinclude a potassium salt, such as potassium oxalate or by the additionof rubidium or cesium in the form of compounds thereof in amounts withinthe range of 0.1 to percent by weight but preferably less than 1 percentby weight, as described in the copending application, Ser. No. 623,528,filed Mar. 16, 1967, and entitled Smoking Products and Process for theirManufacture. Smoke generators for improving the appearance of the smokegenerated by the product can be introduced as by the introduction ofdimethyl tartrate or various fatty acids, esters, ethers and the likeand the aroma and pH characteristics can be achieved by the addition ofvolatilizable alkalyzing material such as ammonium oxalate and the like.

The resulting product is suitable for use as a smoking product alone orin admixture with tobacco to produce a smoking product having goodtaste, good aroma and good appearance.

As the cellulosic raw material, use can be made of various forms ofcellulose, such as wood pulp, alpha-cellulose, flax, fibrouscarbohydrates, seaweed carbohydrates, bamboo filaments, cottonfilaments, hemp, straw, refined paper, rice paper, filamentous gums andeven plants and plant leaves or weeds and the like fibrous or sheetmaterials from which noncarbohydrate components have been separated, allof which is hereinafter referred to as cellulosic material.

It is preferred to make use of a purified cellulosic material from whichvarious of the sugars, proteins, chlorophylls, flavones, colors,lignins, oils, waxes, resins and latices have been removed since thesecontribute undesirable odors and tastes to the smoking product.

Purified cellulose is unsatisfactory for use as a smoking product fromthe standpoint of taste, aroma and burning characteristics. This isbelieved to stem from the acids and aldehydes that are evolved uponpyrolysis of the cellulose. It has been found that many of the defectsof pure cellulose can be greatly alleviated by conversion of themethylol groups to carboxyl groups to produce a product which readilypyrolyzes with complete burning of the cellulosic molecule into watervapor, and oxidation products of carbon such as carbon dioxide and lowmolecular weight compounds which readily volatilize. Thus the object isto achieve selective oxidation of the cellulosic material to convertmethylol groups, primarily the methylol groups containing the C carbon,to carboxyl groups, preferably with better than percent conversion.There is no objection to further oxidation beyond percent by conversionof secondary hydroxyl groups as on C, and C, to monoand diketo groups solong as cleavage does not occur.

It has been found that liquid nitrogen dioxide yields an oxidationreaction that has the desired selectivity and that complete wetting ofthe cellulosic materials can be achieved almost instantaneously withliquid nitrogen dioxide with the result that the oxidation reactiontakes place substantially uniformly throughout the cross section of thecellulosic material and at a much more rapid rate whereby a moreuniformly and more completely oxidized product is obtained in less time.Furthermore, liquid nitrogen dioxide, when used in the proportions mostsuitable for the practice of this invention, operates to quench andimmediately dissipate heat generated by the exothermic reaction so as toavoid the formation of hot spots or nonuniforrnity in the reactions.

In our copending application, Ser. No. 745,221, filed July 16, 1968 now[15. Pat. No. 3,516,416, and entitled "A Smoking Product and Method ofPreparation, description is made of the oxidation of a cellulosicmaterial by suspension in liquid nitrogen dioxide in the ratio of 1 partby weight cellulosic material to 5 to 1,000 parts by weight liquidnitrogen dioxide and preferably 1 part by weight cellulosic material to25 to 50 parts by weight of liquid nitrogen dioxide. The reactiontherein is carried out at a temperature within the range of 15 to 65 C.and at an autogenous pressure when the reaction temperature exceeds 21C. (the boiling point of nitrogen dioxide, N 0

In our copending application, Ser. No. 745,135, filed July 16, 1968, andentitled Preparation of Smoking Product of Cellulose Derivatives andProcess," description is made of the selective oxidation of cellulosicmaterial wherein the oxidation reaction, including reaction rate and theamount of conversion, is materially improved by formulation of theoxidation reaction medium to contain up to 8 percent by weight of waterin the liquid nitrogen dioxide system and by carrying out the reactiontemperatures above 15 C. and preferably within the range of 20 to 45 C.,depending somewhat upon the amount of moisture present in the reactionmedium, whereby the reaction medium is rendered relativelynonelectrically conductive so that the presence of water in the reactionmedium will not result in attack or degradation of the cellulosicmaterial to be oxidized and wherein the formulation to include aqueousmedium in the reaction of liquid nitrogen dioxide operates also toadjust the specific gravity of the reaction medium in the directiontowards the specific gravity of the cellulosic material wherebysuspension of the cellulosic material in the reaction medium is easierto achieve and maintain. The result is a more rapid and uniformoxidation reaction of the cellulosic material to produce a betterproduct at a more rapid rate.

In our copending application, Ser. No. 745,132 filed concurrentlyherewith and entitled Method for Preparation of Smoking Product withSelective Reduction following Selective Oxidation," now U.S. Pat. No.3,478,751 description is made of the treatment of the oxidizedcellulosic material to effect reduction of any nitro groups as well asquinone, ketone and aldehyde groups present in the oxidized cellulosicmaterial or impurities entrained therewith, by treatment with an alkalimetal or alkaline earth metal borohydride or nascent hydrogen at a pHwithin the range of 3 to 7 and at a temperature within the range of to30 C., with the oxidized cellulosic material admised with one to 1,000times its weight of an aqueous solution of the soluble borohydridepresent in a concentration within the range of 0.05 to percent byweight.

In the further copending application, Ser. No. 745,402, filed July 17,1968, and entitled A Smoking Product of Cellulosic Material Subjected toa Nitrogen Dioxide Oxidation and a Mild Oxidation with Peroxide,"description is made of the treatment of the oxidized cellulosic materialwith an alkali metal, alkaline earth metal, or hydrogen peroxide at a pHwithin the range of4 to 6.5 and at a temperature below 50 C. with asolution containing the peroxide in an amount within the range of 0.001to 1 percent by weight.

This invention is addressed to the treatment of the oxidized cellulose,independent of its method of oxidation, and with or without thedescribed borohydride or hydrogen reduction, and with or without thesubsequent mild oxidation with peroxide, further to improve the use ofthe oxidized cellulosic material as smoking product.

It has been found that insufficient ash-forming ingredient in thesmoking product results in a coalescence or coagulation of thepyrolyzing carbohydrates to form a melt of materials during the smokingprocess. The result is a coagulative anaerobic pyrolysis which tends tosmother the fire to the extent that the cigar or pipe or cigarette soonbecomes extinguished. Upon relighting, the smoking product gives a badtaste, at least during the initial puffs, and the smoking product againbecomes extinguished after a very short time thereby to constitute amost undesirable and unacceptable product. Furthermore, this type ofanaerobic pyrolysis produces undesirable muffied bonfire odors.

It is an object of this invention to produce and to provide a method forproducing a smoking product of cellulosic material, and preferablyoxidized cellulosic material, containing ashforming ingredients of atype and concentration to form an ash of sufficient coherence andporosity to enable the ash to build up on the end of the smoking productwithout interfering with or blocking access of air to the burning areathereby to enable the desired burning rate to be maintained; which doesnot introduce undesirable taste or odor to the smoking product or theproduct when smoked; which does not effect thermal breakdown of theoxidized cellulosic material into ketone or aldehyde components whichlend an undesirable odor or taste when burned; in which the ashingcomponents are present in an amount that does not undesirably interferewith the burning rate or pleasure derived from the smoking product, andwhich gives the desired appearance and aesthetic values as derived fromcurrently used tobacco, and especially to pro vide a reticulum adequateto absorb molten oxycellulose so that it does not coagulate into ananaerobically pyrolyzing tarry. mass.

Attempts have been made to employ inertinorganic sub stances, such astalc, perlite, calcined alumina, titanium dioxide and the like fillersas mineralizing agents for ashing purposes but these have not proven tobe sufficiently successful,

when used alone, for various reasons including the inability to hold theash and their tendency to coat around the organic material and encourageanaerobic pyrolysis with consequent smothered bonfire odors.

As described in the aforementioned copending parent applications, thedesired ashing characteristics are provided in a smoking productformulated of cellulosic material, in accordance with the preferredpractice of this invention, by formulation of the cellulosic smokingproduct with calcium or magnesium oxalate. The calcium and magnesiumoxalates have greater thermal stability than the oxidized cellulosicmaterial whereby the latter is burned off first during use of thesmoking product and the calcium or magnesium oxalate, upon combustion ofthe oxidized cellulosic material, breaks down into calcium or magnesiumoxides and carbonates which remain in the ash and carbon monoxide andcarbon dioxide which go off with the smoke. The ash that remains isporous with sufficient coherence to be sustained on the burned end of acigar or pipe or cigarette until flicked off.

While the invention will be described with reference to the use ofcalcium oxalate as the mineralizing or ashing component, it will beunderstood that instead of calcium oxalate use can be made of equivalentamounts of other salts such as are formed of a cation selected from thegroup consisting of alkali and alkaline earth metals, and preferablycalcium and magnesium, and an anion selected from the group consistingof glycolic acid, diglycolic acid or lactic acid, and preferably oxalicacid, tannic acid or pivalic acid. The preferred ashing component iscalcium oxalate and/or magnesium oxalate.

Improvement in the characteristics of the ash left by the burned smokingproduct is achieved when calcium oxalate is present in uniformdistribution in the cellulosic smoking product in an amount as little as1 percent by weight but it is preferred to make use of cellulosicmaterial containing calcium oxalate and/or magnesium oxalate sufficientto give an ash of 15 to 30 percent by weight, calculated on the basis ofcalcium carbonate ash (40 parts by weight of calcium oxalate beingapproximately equivalent to 30 parts by weight of calcium carbonate).When more than 30 percent by weight ash level is present in thecellulosic material, the dilution of the cellulosic material becomesexcessive so that the desired burning or smoking characteristics aredifficult to achieve and it is also difficult to maintain the desiredburning rate, and smothered odors begin to appear.

This application will be addressed to the modification wherein thecellulosic material is in the form of an oxidized cellulose at the timethat the calcium oxalate and the like ashing component is incorporatedinto the smoking product. Such oxidized cellulosic material is apolyuronic acid constituted with a number of uronic groups such asanhydroglucuronic acid and anhydrogalactouronic acid, formed byconversion of methylol groups during the oxidation, and including theketo, diketo and related oxidation derivatives of the uronic acids.

It is the preferred practice of this invention to disperse the calciumoxalate internally within the fibers of the oxidized cellulosicmaterial, although limited benefit can be obtained by the incorporationof calcium oxalate on the outside of the fibers or interstitiallybetween the individual fibers. The distinction between internal andinterstitial ash is an important one in processing and evaluationstudies.

It appears, at present, that the use of calcium or magnesium oxalate ispreferable since such oxalates, when incorporated within the fibers ofthe oxidized cellulosic material, are effective ash-producing agents.Moreover, theoxalates do not have the side effects of producingundesirable odors or of affecting the combustion rate of the material.it isbelieved that the oxalate anion is sufficiently refractory tomaintain the calcium or magnesium as an oxalate while the oxidizedcellulose is undergoing pyrolysis. This prevents the immediate formationof calcium or magnesium polyuronate and the corresponding pyrolyticodor' effects, reminiscent of ketones as produced by the pyrolysis oforganic calcium salts. V

The aforesaid oxalates are insoluble and therefore the problem is toprovide means whereby such normally insoluble ash-forming materials maybe incorporated into the fibers of the oxidized cellulose. We havediscovered a number of ways in which such mineralizing materials can beintroduced into the fibers of the oxidized cellulosic material.

For example, if oxidized cellulose is the starting product,incorporating of the oxalate into the fibers can be achieved by firstsoaking the oxidized cellulose in a soluble mineral salt solution suchas a dilute solution of calcium acetate. The cation readily incorporatesitself into the oxidized cellulosic material to fonn the calcium salt ofthe oxidized cellulose which can be described as a calcium polyuronate.This treatment is followed by a soaking in a solution of oxalic acidwhereby the calcium polyuronate reacts with the oxalic acid whichregenerates the polyuronic acid and produces insoluble calcium oxalateas an internal component inside the oxidized cellulosic fibers. Aceticacid which is formed during the replacement reaction and any excessoxalic acid is removed from the treated cellulosic material by means ofa water wash.

The calcium can be introduced in the dissolved state in an aqueousmedium in which the oxidized cellulosic material is suspended andwherein the calcium ion is made available for reaction to form calciumpolyuronate. For this purpose, the calcium may be introduced as a watersoluble salt such as calcium acetate, calcium chloride, calciumglucuronate, calcium bicarbonate, or the like, but it is preferred tomake the calcium available for reaction with the oxidized cellulosicmaterial by means of dissolving chalk or lime (slaked lime or preferablyquicklime) in an acidic aqueous medium into which the oxidizedcellulosic material is introduced to take up calcium to form calciumpolyuronate. Thereafter oxalic acid is added whereby the oxalic acidwhich diffuses into the fiber is taken up by the calcium to fonn thecalcium oxalate in situ within the cellulosic fiber, and thus toregenerate the oxidized cellulosic material in its original acidiccondition.

When use is made of lime as the source of calcium, the acidic aqueousmedium to which the calcium is added can be formulated from an organicor inorganic acid, such as acetic acid, nitric acid, hydrochloric acid,glucuronic acid and the like, with the acid present in an amount toprovide an acidic solution having a pH less than 7 and preferably a pHwithin the range of 4 to 5. With hydrochloric acid or with acetic acid,the desired level can be obtained with the acid present in the aqueousmedium in an amount within the range of 0.1 to 2 percent by weight.

The pH of the solution into which the oxidized cellulose is introducedshould not exceed 6.5, otherwise the oxidized cellulosic material willtend to dissolve therein. As a result, lime should not be added in anamount which will operate to raise the pH above 6.5 and it is preferredto add lime in an amount to raise the pH of the acidic aqueous medium towithin the range of 4 to 6, and preferably about 5. For this purpose,lime can be added in an amount within the range of 0.01 to 4 percent byweight and preferably in an amount within the range of 0.01 to 1 percentby weight and still more preferably in an amount within the range of0.02 to 0.05 percent by weight. Calcium oxide readily dissolves in theacidic aqueous medium to form the corresponding calcium salt. Theaddition of lime will operate to raise the pH of the solution. To avoidlocalized effects, it is preferred to conduct the calcium replenishmentin a portion of the liquid separate from the portion containing theoxidized cellulose.

The oxidized cellulosic material, after taking up a suitable quantity ofcalcium ion, is then reacted with at least a stoichiometric amount ofoxalic acid in solution in aqueous medium at a pH within the range of 2to 7 and preferably within the range of 3 to 5. Calcium is taken fromthe calcium polyuronate to form the corresponding calcium oxalate insitu in the oxidized cellulosic fibers. Calcium oxalate is comparativelystable by comparison with the oxidized cellulosic material so that it'will remain while the cellulosic material is being pyrolyzed duringsmoking of the smoking product.

The reaction to form the calcium oxalate is not critically dependentupon temperature. However, it is preferred to carry out the describedreaction at a temperature within the range of to 40 C. with a reactiontime of to 10 minutes. Longer times can be used but will be unnecessary.

When in the preferred practice of the invention, use is made of atreating composition containing lime or the corresponding calcium saltsin low amounts, the amount of calcium oxalate formed in situ in theoxidized cellulosic material will be insufficient to provide thepreferred to percent by weight ash level in a single treatment. As aresult, in the preferred practice of this invention, the cycle oftreatment is repeated a number of times to build up the concentration ofcalcium oxalate to the desired level in the smoking product. Byoperating in this way, and avoid too much calcium polyuronate formationat any one time, it is possible to minimize damage to the fiber strengthfrom distortion and embrittlement.

We have found that calcium oxalate and the like mineralizing agents canbe introduced into the oxidized cellulosic fibers by application of afreshly prepared mixture of oxalic acid and calcium salt solutions. Itappears that calcium oxalate remains in the dissolved state for asufficient length of time to achieve substantial impregnation orpenetration of the oxidized cellulosic material before it precipitatesin its insoluble fonn. It is believed that the calcium ions aresufficiently hydrated initially to form a soluble hydrated calciumoxalate which becomes insoluble as the water of hydration separates out.The rate of this dehydration decreases with temperature so that it ispreferred to work at lower temperatures when practicing this concept.The same procedure will be found to be more readily applicable whenworking with magnesium salts for the formation of magnesium oxalate asan ashing component in the smoking product. With magnesium, this agingeffect is much more pronounced.

In practicing this phase of the invention for introduction of calciumand/or magnesium oxalate, use can be made of an aqueous systemcontaining 1 to 15 percent by weight calcium acetate and l to 15 percentby weight oxalic acid dissolved separately in separate increments ofaqueous medium and mixed immediately prior to or during application tothe oxidized cellulosic material. Concentration of acids and saltshigher than 15 percent by weight each should be avoided, otherwise thefibers of the oxidized cellulose may become damaged. Treatment toincorporate the calcium oxalate or magnesium oxalate can be made attemperatures up to C. but lower temperatures from room temperature downto 0 C. are preferred to provide greater margin in the application timebefore separation of the insolubilized oxalate salt occurs. Thecellulosic material should preferably be dry so that it will absorb theimpregnant solution more positively.

Application can be made by spraying the mixture onto. the dry oxidizedcellulosic material with proper agitation for uniform distribution orthe mixture can be added with oxidized cellulosic material into a mixeror homogenizer for uniform distribution. When this technique is employedfor mineralizing the oxidized cellulosic material, the aqueous mixturecan be directly admixed with the oxidized cellulosic material in amountsto provide the desired concentration of calcium oxalate. After themixing, a sufficient aging period must be allowed for theinsolubilization reaction to occur.

With either technique for incorporation of the mineralizing agent in theamounts desired, excess materials can be rinsed from the treatedoxidized cellulosic material with water. The product is then dried.

With the internal mineralizing agent present in the smoking product inan amount within the range of 15 to 30 percent by weight (calculated ascalcium carbonate), it is undesirable to effect complete drying,otherwise the resulting product will be characterized by excessivebrittleness. Instead it is preferred to dry to within the range of 25 to60 percent relative humidity and preferably within the range of 40 topercent relative humidity.

Beneficial results are secured when an acidic component, such as oxalicacid, is reintroduced into the treated oxidized cellulosic material inan amount to provide up to 0.5 percent by weight acid. Such free acidremains to take up residual calcium or other heavy metal ion remainingin the smoking product or released therein during subsequent treatmentor aging or pyrolysis. It probably exists in the system as calciumhydrogen oxalate.

By way of modification, it has been found that a smoking product havingthe desired ashing and smoking characteristics can be secured when thecalcium oxalate, magnesium oxalate, barium oxalate or strontium oxalate,or the corresponding pivalates or tannates are replaced in part by aninorganic filler, such as perlite, talc, titanium dioxide, alumina, orsilica. However, it is undesirable to reduce the calcium oxalate and thelike mineralizing agent to an amount less than percent by weight of thesmoking product. Such inorganic diluents or agents can be admixed drywith the treated smoking product and blended for uniform distribution toprovide a total ashing component which does not exceed 30 percent byweight of the smoking product.

Having described the basic concepts of this invention, examples will nowbe given by way of illustration, but not by way of limitation, of theinvention.

EXAMPLE 1 Oxidized cellulose is introduced into a reaction vessel havinga mixer with sufficient water therein to provide a convenient mobilityof the slurry when stirred. Acetic acid is added to a level of about 2percent by weight acetic acid. Lime is added in an amount to provide anash level of about 5 percent when completely absorbed by the oxidizedcellulose. The pH of the solution thus rises from 4 to about 5. As thecalcium is taken up by the oxidized cellulose, the pH of the system willfall back to about 4. After 5 minutes at ambient temperature, oxalicacid is added in a stoichiometric amount and the pH of the systemimmediately drops to about 3. After 5 to minutes at ambient temperatureand as the oxalic acid is absorbed into the fiber by the calcium to formcalcium oxalate inside the fiber, the pH of the system will rise toabout 4 again.

The cycle is repeated five more times to produce an oxidized cellulosecontaining enough internally dispersed calcium oxalate to give about to24 percent ash when burnt.

After the final cycle, the treated oxidized cellulosic material isthoroughly washed with water containing about 25 percent by weight ethylalcohol, to remove surplus oxalic acid, and the cleansed oxidizedcellulosic material is dried to about 40 percent atmospheric relativehumidity.

After drying, one part by weight of aqueous solution of oxalic aciddissolved in an amount corresponding to 0.25 percent by weight of theoxidized cellulosic material is reintroduced with mixing into two partsby weight of product which is again dried to about 40 to 50 percentatmospheric relative humidity.

EXAMPLE 2 Instead of treating the oxidized cellulose with lime dissolvein the acidic solution, the oxidized cellulose may be treated directlywith an aqueous solution containing about 0.1 percent by weight calciumacetate followed by the introduction of oxalic acid and with furtherprocessing in the manner described in example 1.

EXAMPLE 3 Instead of treating the oxidized cellulosic material with limesolubilized in acidic aqueous medium, as in example I, or with calciumacetate in solution, as in example 2, the oxidized cellulosic materialmay be treated with the calcium oxide or calcium acetate of examples 1or 2 substituted by magnesium, strontium or barium oxide or acetate,respectively, and in corresponding amounts. Instead of making use ofoxalic acid to form the corresponding oxalate, the oxalic acid inexamples 1 and 2 may be substituted by tannic acid to form thecorresponding tannate as the ashing ingredient. The oxalic or other acidcan be introduced in the form of its soluble salts such as sodiumoxalate, ammonium oxalate, sodium tannate, and the like.

EXAMPLE 4 EXAMPLE 5 A 6 percent solution of calcium acetate is providedin one container and a 6 percent solution of oxalic acid is provided inanother and the two solutions are rapidly mixed one with the other in acontainer for immediate spraying with mixing onto purified oxidizedcellulose in amounts calculated to wet the material with its equalweight of liquid. Application is made while the materials are maintainedat a temperature between 0 and 10 C. to provide an oxidized cellulosicmaterial in which the calcium oxalate is formed in situ by reaction ofthe dissolved calcium acetate and oxalic acid inside the fiber. Afteraging the material for an hour to allow the process ro reach completion,the treated oxidized cellulosic material is then thoroughly washed withwater to remove the water solubles including excess acid, and theresulting product is dried to an atmospheric relative humidity of about40 to 50 percent. The ash level will be about 2 percent. It can beincreased to the desired level by repeated treatments.

A 0.1 percent oxalic acid is reintroduced from aqueous solution withmixing into the dried cellulosic material for reaction to take upresidual heavy metal ions present in the smoking product or subsequentlyreleased therein.

In example 5, the calcium acetate can be replaced with correspondingamounts of magnesium acetate, barium acetate, or strontium acetate.Alternatively, instead of the acetates, the alkaline earth salts oflactic or glycolic or glucuronic acid and be used. When magnesium isused, the precipitation reaction is very slow an a very long agingperiod is required, or the material can be dried, after spraying tocomplete the reaction before water washing is applied. Alternatively,water soluble ash generators such as calcium salts of glycolic,diglycolic, lactic or pivalic acid, can be applied by direct spraying ifno subsequent aqueous rinsings are used.

The product of examples 1 to 5 will have smoking characteristics greatlyimproved over cellulosic material alone or the oxidized cellulosicmaterial before treatment in the manner described. It may be preferredfurther to process the treated oxidized cellulosic material produced inaccordance with the practice of examples 1 to 5 as by subjecting thematerials to a selective reduction reaction with borohydride, asdescribed in the aforementioned copending application and/or by themodification of the treating material to incorporate various agents suchas agents for controlling glow and burning rate with the addition ofpotassium, rubidium or cesium salts, as described in the aforementionedparent applications, or the addition of agents for providing smokingneutralizing agents such as ammonia or amine salts, coloring agents andthe like, as described in the aforementioned copending parentapplications.

Beneficial ashing characteristics of limited utility can be achieved byexternal application of such mineralizing agents, as by the introductionof calcium oxalate or others of the described mineralizing agents fromsuspension in aqueous medium for uniform distribution with thecellulosic material or by dry admixture of the mineralizing agent withblending for uniform distribution throughout the smoking product but yit is the preferred concept of this invention to incorporate suchmineralizing agents internally in the oxidized cellulosic smokingproduct.

it will be understood that changes may be made in the details offormulation and operation without departing from the spirit of theinvention, especially as defined in the following claims.

We claim:

1. In the preparation of a smoking product of cellulosic material, thesteps of mineralizing the cellulosic material while in an oxidized stateto provide ash forming ingredients in an amount to make up to 30 percentby weight of the smoking product comprising the steps of treating theoxidized cellulosic material with salt forming solutions containing acation in the form of a heavy metal selected from the group consistingof calcium magnesium, barium, strontium and mixtures thereof, and ananion selected from the group consisting of oxalic, pivalic, tannic,glycolic, diglycolic and lactic acids to form the corresponding salt incombination with the oxidized cellulosic material, and then rinsing anddrying the treated cellulosic material.

2. The process as claimed in claim 1 in which the oxidized cellulose isfirst treated with the cation in aqueous solution whereby the cationattaches to polyuronic acids of the oxidized cellulosic material to forma corresponding salt, and then with the anion in-aqueous solution forreaction with the cation to form the corresponding insoluble salt.

3. The process as claimed in claim 2 in which the aqueous solutioncontaining the cation has a pH less than 6.5.

4. The process as claimed in claim 2 in which the aqueous solutioncontaining the cation has a pH of 4 to 5.

5. The process as claimed in claim 2 in which the aqueous solutioncontaining the anion has a pH within the range of 2 to 7.

6. The process as claimed in claim 2 in which the aqueous solutioncontaining the anion has a pH within the range of 3 to 5.

7. The process as claimed in claim 2 in which the aqueous solutioncontaining the cation is formed by mixing the oxide of the metal inaqueous medium with an acidic component to take the oxide into solution.

8. The process as claimed in claim 7 in which the cation is introducedas lime.

9. The process as claimed in claim 8 in which the lime is present in anamount within the range of 0.1 to 4.0 percent by weight.

10. The process as claimed in claim 8 in which the lime is present in anamount within the range of 0.01 to l percent by weight.

11. The process as claimed in claim 7 in which the acid solutioncontains 0.01 to 2.0 percent by weight of acid.

12. The process as claimed in claim 7 in which the acid is in the formof acetic acid.

13. The process as claimed in claim 1 in which the salt forming solutionwith which the oxidized cellulosic material is treated is formed offreshly mixed solutions of a water soluble salt of the cation and awater solution of the acid but in which the salt formed of the cationand anion remains in the dissolved state for a sufficient period of timeto enable penetration of the oxidized cellulosic material beforeprecipitation.

14. The process as claimed in claim 13 in which the cation is selectedfrom the group consisting of calcium and magnesium and in which theanion is selected from the group consisting of oxalic, tannic andpivalic acid.

15. The process as claimed in claim 14 in which the cation is present inthe solution in an amount within the range of l to 15 percent by weightand in which the anion is present in the solution in an amount withinthe range of l to 15 percent by weight.

16. The process as claimed in claim 13 in which the cellulosic materialis treated with the solution at a temperature between ambient and 0 C.

17. The process as claimed in claim 1 in which the treated oxidizedcellulosic material is dried to a relative humidity of 25 to 60 percent.l

18. The process as claimed in claim 1 in which the treated oxidizedcellulosic material is dried to a relative humidity of 40 to 50 percent.

19. The process as claimed in claim 1 in which the treatment is repeateda number of times until the mineralizing salts are built up in theoxidized cellulosic material to a desired level within the range of 15to 30 percent by cation- 20. The process as claimed in claim 1 whichincludes a a part of the mineralizing agent an inorganic filler selectedfrom the group consisting of perlite, talc, titanium dioxide, aluminaand silica in amounts to replace up to 5 percent by weight of the cationanion salt formed in situ in the oxidized cellulosic material.

21. The process as claimed in claim 1 which includes adding an aqueoussolution of an acid to the treated oxidized cellulosic material in anamount to provide the oxidized cellulosic material with up to 0.5percent by weight of the acid and in which the acid is selected from thegroup consisting of oxalic acid, pivalic acid and tannic acid, and inwhich the free acid remains to take up residual heavy metal ionsremaining or released in the smoking product.

22. A smoking product produced by the method of claim 1 23. A smokingproduct produced by the method of claim 21.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 559Dated September 28, 1971 Inventor(s) Theodore Br kln et al in theaboveidentified patent It is certified that error appears corrected asshown below:

and that said Letters Patent are hereby Column 8, line 30, change "1:0"to "to";

Column 8, line 44, change "and" to "can";

Column 10, line 32, change "cation" to "weight";

Column 10, line 33, change "a a" to "as a" Signed and sealed this llthday of April 1972.

(SEAL) Attest:

EDWARD.M.FLETCHER ,JR. ROBERT GOTTSCHALK Attestlng Officer Commissionerof Patents FORM PO-IOSO (10-69) USCOMM DC 503764369 u 5 GOVERNMENTPRINTING ornc: 1 I9l9 o-ass-su

2. The process as claimed in claim 1 in which the oxidized cellulose isfirst treated with the cation in aqueous solution whereby the cationattaches to polyuronic acids of the oxidized cellulosic material to forma corresponding salt, and then with the anion in aqueous solution forreaction with the cation to form the corresponding insoluble salt. 3.The process as claimed in claim 2 in which the aqueous solutioncontaining the cation has a pH less than 6.5.
 4. The process as claimedin claim 2 in which the aqueous solution containing the cation has a pHof 4 to
 5. 5. The process as claimed in claim 2 in which the aqueoussolution containing the anion has a pH within the range of 2 to
 7. 6.The process as claimed in claim 2 in which the aqueous solutioncontaining the anion has a pH within the range of 3 to
 5. 7. The processas claimed in claim 2 in which the aqueous solution containing thecation is formed by mixing the oxide of the metal in aqueous medium withan acidic component to take the oxide into solution.
 8. The process asclaimed in claim 7 in which the cation is introduced as lime.
 9. Theprocess as claimed in claim 8 in which the lime is present in an amountwithin the range of 0.1 to 4.0 percent by weight.
 10. The process asclaimed in claim 8 in which the lime is present in an amount within therange of 0.01 to 1 percent by weight.
 11. The process as claimed inclaim 7 in which the acid solution contains 0.01 to 2.0 percent byweight of acid.
 12. The process as claimed in claim 7 in which the acidis in the form of acetic acid.
 13. The process as claimed in claim 1 inwhich the salt forming solution with which the oxidized cellulosicmaterial is treated is formed of freshly mixed solutions of a watersoluble salt of the cation and a water solution of the acid but in whichthe salt formed of the cation and anion remains in the dissolved statefor a sufficient period of time to enable penetration of the oxidizedcellulosic material before precipitation.
 14. The process as claimed inclaim 13 in which the cation is selected from the group consisting ofcalcium and magnesium and in which the anion is selected from the groupconsisting of oxalic, tannic and pivalic acid.
 15. The process asclaimed in claim 14 in which the cation is present in the solution in anamount within the range of 1 to 15 percent by weight and in which theanion is present in the solution in an amount within the range of 1 to15 percent by weight.
 16. The process as claimed in claim 13 in whichthe cellulosic material is treated with the solution at a temperaturebetween ambient and 0* C.
 17. The process as claimed in claim 1 in whichthe treated oxidized cellulosic material is dried to a relative humidityof 25 to 60 percent.
 18. The process as claimed in claim 1 in which thEtreated oxidized cellulosic material is dried to a relative humidity of40 to 50 percent.
 19. The process as claimed in claim 1 in which thetreatment is repeated a number of times until the mineralizing salts arebuilt up in the oxidized cellulosic material to a desired level withinthe range of 15 to 30 percent by weight.
 20. The process as claimed inclaim 1 which includes as a part of the mineralizing agent an inorganicfiller selected from the group consisting of perlite, talc, titaniumdioxide, alumina and silica in amounts to replace up to 5 percent byweight of the cation - anion salt formed in situ in the oxidizedcellulosic material.
 21. The process as claimed in claim 1 whichincludes adding an aqueous solution of an acid to the treated oxidizedcellulosic material in an amount to provide the oxidized cellulosicmaterial with up to 0.5 percent by weight of the acid and in which theacid is selected from the group consisting of oxalic acid, pivalic acidand tannic acid, and in which the free acid remains to take up residualheavy metal ions remaining or released in the smoking product.
 22. Asmoking product produced by the method of claim
 1. 23. A smoking productproduced by the method of claim 21.